Looking Ahead

Forages & Grains

Corn

Soybeans

Fruits

Vegetables

Nursery & Forest

Degree Days

Weeds
Volume 57 Number 15 Date 07/26/2012


PURSELANE - This, drought-tolerant, annual plant has become increasingly common in home gardens and landscaped areas. Purselane is easily identified by its smooth, prostrate growing purplish-red stem and thick succulent leaves. Because it reproduces from seeds and stem pieces, long-term control requires removing entire plants prior to seed production for several years in a row.

GIANT RAGWEED - Recent surveys in row crops indicate that giant ragweed control was ineffective in many fields again this season. Unsatisfactory control of this summer annual usually results from a combination of its competitive characteristics (i.e. early seedling emergence, staggered emergence times, and rapid growth rate) and failed management programs. In addition, prevailing drought conditions have also contributed to poor control this year.

Giant ragweed is well adapted to survive newer agronomic practices, such as earlier planting and reduced tillage. The most consistent control programs are those that combine a sequential management approach that includes the use of both preemergence (PRE) and postemergence (POST) herbicide applications. Guidelines for giant ragweed management include the following:

• Control weeds that emerge prior to planting with tillage or a preplant burndown application.
  
  
• Apply PRE herbicides with activity on giant ragweed to reduce competition with crops, provide flexibility in the timing of POST applications, and minimize the need for additional POST glyphosate applications.
  
  
• Where a PRE herbicide is used, apply POST herbicides before plants are 6-10 inches tall. If a PRE is not used, apply when giant ragweed is less than 6 inches tall. With most non-glyphosate herbicides, applications should be made prior to 4 inches tall.
  
  
• Scout fields two weeks after the POST application. Control escapes or plants that emerge after the initial POST application with a second POST application.

--Clarissa Hammond, DATCP Weed Scientist